EMPLOYEE BENEFIT PLANS - Narrative (Details) $ in Millions	12 Months Ended
	Oct. 31, 2025 USD ($) plan	Oct. 31, 2024 USD ($)	Oct. 31, 2023 USD ($)
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Expected return on assets	$ 0.0	$ 0.0	$ 0.2
Net periodic benefit cost	0.8	0.8	0.6
Expected future benefit payments	$ 11.3
Number of defined contribution plans | plan	3
Cost recognized	$ 32.1	30.6	29.8
Multiemployer Plans, Postretirement Benefit Plans
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Contributions by ABM	446.7	434.1	441.8
Defined Contribution Plans
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Cost recognized	59.0	54.5	59.2
Rabbi Trust
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Fair value deferred compensation plan assets	4.8	4.4
Deferred Compensation Plans
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Total liability of deferred compensation	27.4	26.7
Compensation expense	$ 0.7	$ 0.6	$ 0.5